Tuesday, June 5, 2012

Disputes Over the Mechanism of Evolution Distract from the Fact That Evidence for Common Descent is Voluminous

This a comment that I made on the Biologos blog (http://biologos.org/blog) in response to a post by James K. Dew in the series Southern Baptist Voices (http://biologos.org/blog/southern-baptist-voices-theistic-evolution-and-intelligent-design) Dr. Dew's post was titled Teleological Arguments, Theistic Evolution and Intelligent Design. He covered several points, but I am only responding to his point that conservative (Southern Baptist) theologians don't accept that "macroevolution" happened.

I am going to respond here to Dr. Dew's statement that he and his colleagues aren't convinced that evolution (common descent) is true.

Most of the discussion that goes on on this site and others concerns the mechanism(s) of evolution - the assertion by many that the standard mechanisms of mutation and natural selection combined with drift etc. are inadequate; thus some form of ID, from special creation to micromiracles during evolution must be invoked. Although it is commonly conceded that ID is compatible with common descent, the only one of the prominent supporters of ID that I am aware of who accepts common descent (and I think not incidentally the only one of the ID advocates who has ever been a full-fledged researcher in biological science) is Michael Behe. Thus, the implicit argument seems to be that since the generally accepted mechanisms for evolution are asserted to be inadequate, therefore common descent is not true. Of course this is inconsistent with the admission that ID is compatible with common descent, but since nearly everyone who advocates ID rejects common descent, it makes me wonder what they really think.

The trouble with the focus on the adequacy or not of mechanisms of evolution is that there is a huge mass of evidence that common descent is true that does not depend on knowing what the mechanism of evolution is.

When the evidence for common descent (largely from comparative genomics) is discussed on this site and others, the rationalizations given for rejecting it are, I'm sorry to say, laughable, regardless of the graduate degrees of the people making the rationalizations. When those arguments have been demolished by Drs. Venema, Falk and others, the pattern is that the people who made them don't respond. They just go back to telling laymen (and theologians) that there is nothing to be concerned about in evolution, and, in essence, "here are my credentials to prove it." I have to confess that it has been something of a shock to me that there are people smart enough to get graduate degrees in science who nonetheless can't admit to themselves that their position isn't really determined by weighing evidence - it is determined by a prior theological/Biblical/philosophical committment, and they view their scientific training simply as preparing them to come up with rationalizations for rejecting evidence, knowing their credentials alone will be enough to convince non-scientists who just want the whole thing to go away.

What evangelical theologians need to understand is, quite apart from knowing anything or everything about the mechanism of evolution, we now have a huge amount of evidence that common descent is true. Dr. Dembski said in his post that the evidence for common descent is "mixed." No, it really isn't. It may be rather complicated to define exactly what the relationship of humans is to a bacterium, since it has been a very long time since a common ancestor and many complicated things have happened to the DNA of both lines since then. But defining the relationship of humans to other primates really isn't very complicated at all. We have a common ancestor with chimps a few million years ago and with other primates somewhat further back than that.

If you want to know what the relevant evidence is, some of it is summarized on this website. I have summarized some of it that I am familiar with on my blog The Art of the Soluble (http://biomattersarising.blogspot.com/)  I think it is easily comprehensible by anyone with a little knowledge of modern genetics. In general the evidence consists of a very large number (conservatively, hundreds of thousands) of transposable element insertions and other mutations that are complex enough to be easily recognizable in genomes and extremely unlikely to have occurred in parallel in two or more related species. These mutations individually are present at exactly corresponding positions in the genomes of different species. The fact that these insertions often occur on top of previous insertions means that not only can the presence of the same insertion in different species be determined, it is apparent that the insertions occurred in the same order in the different species. On top of that, the pattern of presence or absence of insertions at particular sites in the genomes of different species is consistent with individual insertions happening at particular points during the evolution of primate species. (i.e. If an insertion happened after the branching of New World monkeys but before the branching of the various apes, it is present in the expected ape and human species and absent in the rest.) This kind of evidence for common ancestry of humans with other primates is particularly clear because speciation of humans and other primates occurred very recently in evolutionary time so the accumulation of mutations has not had time to obscure the evidence.

The simple fact of common ancestry with other primates brings up all the problems that need to be dealt with by theologians and Bible scholars. The mechanisms of evolution will continue to be matters of argument among biologists and philosophers for a long time, and theological speculations about possible mechanisms of divine creation and action will go on indefinitely. The necessity to deal with the implications of common ancestry does not depend on the mechanism of evolution or divine action, although these things will undoubtedly be part of that discussion. The bottom line is that evangelical theologians need to come to terms with common ancestry, or continue to gain a reputation (sorry to be blunt) for indulging in a remarkable degree of self-delusion.  It is past time to quit hiding behind the credentials of a few people who make ridiculous arguments against common descent in the face of the huge amount of evidence that exists and deal with the situation that this evidence has created.

I guess I should add, since credentials seem to matter, that I am a life-long evangelical who went to med school and grad school, got a Ph.D in biochemistry and did research for several decades. I'm sorry if I seem to be somewhat harsh about this, but I'm convinced that evangelical academics are not doing themselves or the church (or God) any favors by refusing to deal with this issue.